Golay-Coded Excitations for Rotational Intravascular Ultrasound Imaging

Abstract

Intravascular ultrasound (IVUS) imaging employs high imaging frequencies (from 20 to 60 MHz) to visualize microvascular structures by sacrificing the depth of penetration with an increased signal attenuation. To compensate for the reduced echo signal-to-noise ratio, chirp-coded excitations, which require complex system configurations in high-frequency ultrasound imaging, are considered as suitable methods for rotational IVUS. Golay-coded excitations, which only need simple electronics and have no range sidelobe artifacts if the incident locations of the Golay pair are the same, have not been considered for rotational IVUS. In this study, computer simulations and experiments with a custom-made IVUS imaging system running at 30 fps are performed to investigate on the optimal operational conditions of Golay-coded excitations in rotational IVUS imaging. While the code length was not a significant factor affecting the range sidelobe level (RSLL), a change in the imaging frequency from 25 MHz to 66 MHz increased the RSLL from -65 dB to -45 dB with 2048 beamlines. In addition, an increase in the number of beamlines from 64 to 2048 reduced the RSLL from -17 dB to -50 dB in the simulation and from -14 dB dB to -38 dB in the experiment. To further decrease the RSLL, a weighted averaging method that compressed the coded pulse was proposed. The RSLL could be suppressed from -50 dB to -80 dB and from -38 dB to -53 dB in the simulation and experiment, respectively. Golay-coded excitation imaging was also successfully demonstrated on freshly harvested pig coronary arteries.